[build-presets] Disable SourceKit-LSP tests on Linux Incremental

rdar://89359439

Author: hamishknight

utils/build-presets.ini

@@ -1113,6 +1113,8 @@ swiftsyntax
 swiftsyntax-verify-generated-files
 indexstore-db
 sourcekit-lsp
+# SourceKit-LSP tests are flaky on Linux, disable them until we have fixed the root cause - rdar://89359439
+skip-test-sourcekit-lsp
 install-llvm
 install-swift
 install-llbuild